Tuning device



Oct. 16, 1956 F- w. SCHMIDT, JR., ET AL 2,767,381

TUNING DEVICE Filed June 20, 1951 INVENTORS FRED w. SCHMIDT, JR. By SYLVESTER A. DEM/1R5 A TTORNE Y5 86 Fig. /2

limited States Patent 2,767,381 TUNING DEVICE Fred W. Schmidt, Jr., Cedar Grove, and Sylvester A. De Mars, Ridgewood, N. J., assignors to Allen B. Du Mont Laboratories, Inc., Clifton, N. J., a corporation of Delaware Application June 20, 1951, Serial No. 232,537 1 Claim. (Cl. 336-79) This invention relates to an electric tuning element for resonating radio frequency energies at various selectable frequencies, particularly useful for television.

It is among the objects of the invention to provide a tuner for radio frequency energies which is compact, easily constructed, economical, which has a wide tuning range, and which avoids the use of sliding contacts. Other objects will be apparent.

Figure 1 is a perspective view of a tuning element incorporating the basic principles of the invention.

Figures 2 and 3 show perspective views of a portion of Figure 1.

Figure 4 shows a top elevational view of Figure 1.

Figure 5 is a cross-sectional view through 55 of Figure 4.

Figure 6 is a top elevational View of an alternative embodiment of the invention.

Figure 7 is a cross-sectional view through 77 of Figure 6.

Figure 8 is a schematic diagram of an electric circuit embodying the invention.

Figure 9 shows a switch construction incorporated with the invention.

Figures 10, l1 and 12 are side elevational views of a complete tuning element and housing therefor.

In Figure l, a hollow insulative cylinder 11 has tuning coils 12 and 13 attached thereto, each of which is constructed in a spiral manner and'lying in a plane curved to fit the contour of the cylinder 11.

The coil 12 is provided with lead wires 14 and 15. A rotatable assembly 16, positioned within the cylinder 11 comprises an insulative cylinder 17, having an outer diameter slightly smaller than the inner diameter of the hollow cylinder 11, and a tuning shaft 18.

The cylinder 17 is an elongated member having one or more metallic layers embedded in the outer surface thereof. These metallic layers represent tuning elements which move into and out of the electrical field of the spiral coils 12 and 13 as the cylinder 17 is rotated within the hollow cylinder 11. These tuning elements, as may be seen in Figures 2 and 3, may also be part of the surface of the cylinder 17. One of the elements 21 may be of a ferrous material such as iron. Another of the elements, such as 22, is of a non-ferrous material such as copper or aluminum. These elements 21 and 22 are positioned longitudinally on the cylinder 17 in a position corresponding to the longitudinal position of the coil 12 on the hollow cylinder 11. Thus when the cylinder 17 is placed within the cylinder 11 and rotated therein, the two tuning elements 21 and 22 alternately enter the field of the coil 12.

If desired, the surface of the cylinder 11 may be of iron material such as powdered iron, in which event the non-ferrous tuning element 22 may be a metallic layer of copper or aluminum secured to or embedded within the surface of the cylinder-17. -Alternatively, as pointed out above, both elements may be metallic plates.

which may be 2,767,381 Patented Oct. 16, 1956 A second pair of tuning elements, 23 and 24, may be positioned on the surface of the cylinder 11 corresponding to the longitudinal position of the second coil 13 on the cylinder 11. As before, one of the second pair of tuning elements, such as that illustrated at 23, is of ferrous material, while the other element 24, comprising the pair, is of non-ferrous material. Thus, as the cylinder 17 is rotated within the cylinder 11, both spiral coils 12 and 13 are tuned.

The tuning elements described above may have irregular shaps, as shown. These irregularities in the shape or edges of the tuning elements, are for tracking purposes and a particular shape or irregularity is chosen, depending on the particular tracking problem involved in the apparatus in which this tuning element is being used. Such tracking principles are in themselves well known to those skilled in the art and these known principles may be used in determining the irregular shape of the novel tuning elements described above.

in the embodiment shown in Figure 3, one tuning element 31, which may be of non-ferrous material, representing a layer of copper, for instance, is positioned on the surface of the cylinder 17 and is elongated in shape so as to cover a substantial longitudinal portion of the surface of the cylinder 17, thereby to lie simultaneously within the electric fields of both the spiral coils 12 and 13 on the cylinder 11. The second tuning element 32 is of ferrous material and, like the other element 31 comprising the pair, extends along the surface of the cylinder 17 so as to lie within the electric fields of both the spiral coils 12 and 13 or" the cylinder 11. In this way the tuning elements 31 and 32 tune the two spiral coils 12 and 13. As before, the shape or edges of these elongated tuning elements 31 and 32, may be irregular for tracking adjustments. It will be noted that one end 36 of the tuning element 31 may extend as shown at 33 to overlap somewhat the complimentary edge 37 of the tuning element 32. Similarly, one point 34 of the end 37 of the element 32 may extend to overlap slightly the edge 36 of the tuning element 31.

Additional spiral coils may be secured to the surface of the cylinder 11 as illustrated in Figure 4. These additional tuning coils 41 and 42 likewise lying in a plane conforming to the surface of the cylinder 11, are positioned preferably on the diametrically opposite surface thereof from that position of the coils 12 and 13. Also preferably they are positioned longitudinally opposite the coils 12 and 13. Those skilled in the art, however, may prefer slight modification of the positioning of these coils in accordance with particular tuning problems encountered. A cross sectional view of these coils is shown in Figure 5. The additional coils 41 and 42 have lead lines for connection to electrical circuits as illustrated in Figure 5 in which coil 41 has leads 43 and 44.

Modifications of the shape of the tuning elements on the surface of the rotatable cylinder are shown in Figures 6 and 7. As illustrated, one element 47 may be substantially square in shape. A second element 48 has a longer dimension circumferentially about the surface of the cylinder 17. A third tuning element 49 may be relatively small in area as compared to the other tuning elements on the cylinder. A fourth tuning element 50 may be used having a different dimension or shape, depending upon the particular tuning and tracking desired. A fifth tuning element 51 is shown comprising a threaded metallic element which when rotated will move radially so as to vary in its radial position relative to the outer surface of the cylinder 17.

The schematic circuit of Figure 8 is a preferred electric arrangement of the construction shown in Figures 4 and 5. A connector terminal 61 is connected to the lead Wire 15 of the coil 12 and to a first contact 62 of a s witch 63. The other lead wire 14 of the coil 12 is connected to a switching terminal 66 of the switch 63, a first trimming capacitor 67, the other side of which is grounded, and to the lead wire 44 from the coil 41. The other lead wire 43 from coil 41 is connected to an output or connector terminal 71, a second trimming capacitor 72, the other side of which is grounded, and to a second contact 73 of said switch 63 As may be seen in Figure 9, the switch 63 is actuated by means of a cam 76 located on or integral with the rotatable cylinder 17 or tuning shaft 13, which causes the switching lever 77 to engage electrically either of the switch contacts 62 or 73 in accordance with the position of the tuning shaft.

In the preferred embodiment of Figures 19, ll and 12, a housing 81 supports the tuning coils 12 and 41, the rotatable tuning cylinder 17, the capacitors 67 and 72, and the switch 63. This housing 81 is shown attached to a chassis 82 by any convenient means. Each of the capacitors 67 and 72 comprises a conductive cylinder within which extend adjusting screws 86 and 37 respectively. The screws 86 and 87 are threaded in chassis 82 and the capacitances can be varied by varying the length of or extension of the screws within the cyl inders. In this embodiment the switch 63 comprises conductive members 91, 92 and 93 which may be plated or. sprayed on a surface of one end of the housing 81. One conductive member 92 has an annular portion 96, concentric with the axis of the tuning shaft 18, and a connector tab 97 which corresponds to the terminal 66 shown in Figure 8. The other conductive members 91 and 92 have outer concentric portions 98 and 99 respectively, concentrically encircling the annular portion 96 of member 92. Each of the members 91 and 93 is provided with connector terminals 191 and 102 respectively which correspond with the contacts 62 and 73 of- Figure 8. Attached to the rotatable shaft 18 is a rotatable slider member 106 having at the extremities thereof sliding contacts 107 and 108 which electrically and slidably engage the concentric member 96 and the other concentric members 98 and 99 respectively. This switch functions to connect selectively the terminal 97 With'either the terminal 161 or the terminal 102. Thus the coils 12 and 41 may be switched into the cireuit individuallyfor together in series.

The operation is asfollows:

Referring to embodiment shown in Figure 4 and particularlyv to the coils 12 and 41 thereof, coil 12 may be constructed to have an inductance so as to be tuneable over the frequencies comprising the present standard low-frequency television channels and FM frequencies, The coil 41 may be constructed to have an inductance so as to be tuneable over the frequency range of the presently standard high-band television channels. However, it is to be understood that said coils may be designed to tune over other desired ranges of frequencies; viz., the present VHF television channels and the proposed UHF television channels. The resonance frequency of each of said coils is lowered when the ferrous tuning element is positioned adjacent thereto, and is raised when the non-ferrous tuning element is positioned adjacent thereto. By rotating the ferrous and non-ferrous tuning elements as has been described, it is found that each of the elements can be made to tune each of the coils over a two-to-one frequency range; the combined effects of the ferrous and non-ferrous tuning elements have been found to provide a tuning range of four-to-one.

With the tuning elements positioned on a rotatable cylinder as shown, one-half revolution of the cylinder'can tune one of the coils over its four-to-one range; e. if the beginning position of the rotatable cylinder is such 1556 the ferrous element is adjacent the tuning coil, the coil will be tuned to its lowest frequency; one-half revolution of said cylinder will progressively raisc the tuning frequency as the ferrous element is moved from and the non-ferrous element is moved towards the coil; the coil being tuned to its highest frequency when the nonferrous element is immediately adjacent it. At this moment of rotation, the ferrous element will be immediately adjacent the other of the tuning coils, whereupon the switch functions to switch the other coil into the circuit, the other coil now being tuned to its lowest frequency. Continued rotation of the inner cylinder raises the tuning frequency of the other coil until it is at its highest frequency one-half revolution later when the non-ferrous element is positioned immediately adjacent thereto. Thus, one revolution of the inner cylinder tunes the device through its entire range. Switch 63 may be a single pole, single throw switch adapted selectively to connect or short-circuit the larger of the tuning coils, the smaller of the tuning coils being so small as not to have an appreciable efiect on the tuning of the larger coil, even though the smaller coil is left connected in the circuit at all times.

Tracking, or the rate of change of tuning, may be controlled by providing irregular shapes along the edges or around the peripheries of the tuning elements as indicated at 26, 33 and 34 of Figures 2 and 3. Adjacent end portions of these elements may be overlapped, as indicated at 27, 28, 36, and 37, to provide tracking. As shown in Figure 4, one of the tuning coils 41 may be axially offset from the other tuning coil 12; the circumferential edges of the tuning elements 21 and 2 2 that are nearest the, coil 12 may be shaped to provide tracking of the coil without affecting the tracking of the other coil 41. Similarly, the other circumferential edges of the elements 21 and 22 may be shaped to provide tracking of the coil 41 without affecting the tracking of the offset coil 12.

While the circuit has been described particularly with reference to coils 12 and 41 of Figure 4, other sets of coils 13 and 42 of Figure 4 may be employed in other parts of the circuits, thus providing ganged tuning of a plurality of circuits.

Although the preferred embodiment comprises two coils arranged around the periphery of rotation of the ferrous and non-ferrous tuning elements, it will be evident that a plurality of any desired number of coils may be thus employed. Various alternative switch arrangements may be used to connect the coils into the circuit as desired. I

Although the rotatable tuning cylinder 17 is described as preferably being an insulative member having attached thereto the conductive tuning elements 21 and 22, it has been found satisfactory to construct the rotatable cylinder of a ferrous material and to attach to a portion of and overlying the surface thereof a nonferrous tuning element, of the desired shape, by any known means. Alternatively, the cylinder may be made of a non-ferrous material and a portion of the peripheral surface thereof may be overlain with a ferrous material.

Referring to Figures 6 and 7, the rotatable cylinder 46 may be employed in the manner of a detent-switch device whereby the cylinder snaps into place at each position of a tuning element adjacent the coil 56. Adjustable tuning may be provided for the tuning elements by the construction shown for the element 51 which comprises a cylindrically threaded screw of ferrous or non-ferrous material having a slot 59 by means of which said element 51 may be varied in radial position, thus adjusting the relative proximity of the element 51 to the coil 56 when in position with respect thereto. The center region of the spiral coil 56 may be left open to pro vide access with the adjusting tool to the tuning element 51 in order thatthe tuning of the coil may be adjusted while said element 51 is. switched in position adjacent the coil.

The tuning range of the circuit shown in Figure 8 may be adjusted by means of the condensers 67 and 72, which are shown, in Figures 10 and 11, in novel combination with the tuner housing 81. Adjusting ofthe screws 86 and 87 effects the tuning of the condensers 67 and 72.

While the present invention has been described in its basic form and in a preferred arrangement, it will be evident that alternative embodiments may be employed within the scope thereof.

What is claimed is:

Electrical tuning apparatus comprising a pair of spiralshaped coils curved about an axis and axially offset from each other, and a tuning element curved about said axis and positioned to be rotated about said axis selectively near said coils and having a first tapered circumferential References Cited in the file of this patent UNITED STATES PATENTS 2,018,231 Rochow Oct. 22, 1935 2,406,720 Van Loon Aug. 27, 1946 2,422,995 Vorie June 24, 1947 2,431,425 Sands Nov. 25, 1947 

